JP2663811B2 - Manufacturing method of aluminum clad steel sheet - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing an aluminum clad steel sheet as a composite material of carbon steel and aluminum (including an aluminum alloy).

[0002]

2. Description of the Related Art Aluminum / carbon steel clad plates having both the characteristics of "aluminum", which has good corrosion resistance and light weight, and "carbon steel", which has high strength and high formability and are inexpensive, have recently been used as building materials. In addition, it is also important as a material for the reaction plate of a linear motor car, and its use is expanding more and more, as its use is being studied as part of measures to reduce the weight of automobiles. .

[0003] By the way, such an aluminum clad steel sheet in which carbon steel and aluminum are combined is industrially manufactured by cold rolling in which an aluminum material sheet heated and heated and superimposed on a carbon steel material sheet at normal temperature is joined and rolled. It is generally manufactured by the "rolling method".

[0004] However, in the above-described method of heating only the aluminum material plate and superimposing it on a carbon steel plate at room temperature and pressing it, if the thickness of the aluminum material plate is as thin as 1.5 mm or less, for example, Even if the superimposition is performed immediately before the rolling mill, the temperature drop at the contact surfaces of both materials becomes large and it is not possible to achieve sufficient joining. There is a problem that the curing becomes large. In this way, work-hardened clad products tend to crack or break when subjected to forming processes such as "deep drawing" or "overhanging", and therefore have to be said to be unsuitable for forming. .

[0005] The work hardening material can be adjusted by performing soft annealing if it is a "single material".
In the case of an aluminum-clad steel sheet, the melting point of aluminum is low, so that heating to a temperature at which the carbon steel is softened causes the melting of the aluminum, so that it was difficult to apply softening annealing. Particularly, in the joining rolling by the cold rolling method, the rolling reduction required for the pressure bonding is extremely high, and the work hardening of the obtained product is much larger, so that it is not suitable as a forming material.

Accordingly, an object of the present invention is to establish a low-cost and stable means for mass-producing aluminum-clad steel sheets having sufficient bonding strength and good formability. Was.

[0007]

Means for Solving the Problems The present inventors have conducted intensive studies in order to achieve the above object, and have obtained the following findings. a) To produce an aluminum-clad steel sheet with high joining strength and low work hardening by a rolling method that is excellent in mass productivity, the joining surface temperature of both carbon steel and aluminum materials during joining rolling should be kept as high as possible. It is important to increase not only the temperature of the aluminum material plate but also the temperature of the carbon steel material plate.

B) However, conventionally, when a carbon steel material plate is heated in an air atmosphere, a scale is generated on the surface (joining surface), which leads to a decrease in bonding strength. Although it was thought that it was not appropriate, even if the carbon steel material plate was heated to a temperature that enabled “reduction of rolling reduction”, which leads to a reduction in work hardening, and sufficient bonding strength was obtained, If, during this time, the time during which the carbon steel material plate is kept at a high temperature above a specific temperature is limited for a short time, scale growth will be small even in the atmosphere, and the joining will not be hindered.

The present invention has been completed after further study based on the above findings and the like. "A carbon steel sheet and an aluminum sheet (including an aluminum alloy) are overlapped and roll-pressed to produce a clad sheet. In order to do the
Heated to 70-250 ° C, this steel plate and 300-500 ° C
While the aluminum plate heated is superimposed on the steel plate and the carbon steel plate is subjected to joining rolling at a temperature not lower than 170 ° C., the carbon steel plate before being heated and rolled is 1
The above-mentioned joining rolling is performed by limiting the time in the temperature state of 70 ° C. or more to within 2 minutes, or, after this joining rolling, the holding temperature is 250 to 450 ° C., and the holding time is 5 minutes. By performing the above heat treatment, it is possible to stably produce an aluminum-clad steel sheet having high joining strength and good formability. "

FIG. 1 is a graph illustrating “an example of a change in temperature of a carbon steel sheet until joining rolling” according to the present invention.

[0011]

According to the method of the present invention, the carbon steel sheet is heated to 170 to 250 ° C. prior to joining and rolling. If the heating temperature is lower than 170 ° C., the carbon steel sheet is heated to 170 ° C. or more during joining and rolling. The temperature of the material plate cannot be ensured, so the temperature of the joint surface with the aluminum material plate is low, and the rolling reduction required for joining becomes extremely large, and the work hardening of the product clad material is remarkable and the desired formability is obtained. Can not secure. Further, the upper limit of the heating temperature is set to 250 ° C. because the surface is rapidly oxidized at a higher temperature and the scale is increased.
This is because the metal grows and sufficient bonding strength cannot be obtained.

The reason why the "time during which the carbon steel sheet material is kept at a temperature of 170 ° C. or more before being heated and rolled" is limited to 2 minutes or less because the high temperature state is longer than 2 minutes. If the temperature is maintained over the range, the oxidation of the surface proceeds, and the surface grows to a scale that hinders the junction.

On the other hand, the heating temperature of the aluminum material plate before the joining rolling is 300 to 500 ° C. If the heating temperature is lower than 300 ° C., the rolling reduction required for the joining is also high, and the material is heated. It should be avoided because work hardening becomes large and causes deterioration of the moldability of the product. 500 ° C
When the aluminum material is heated to a temperature exceeding the above range, the material becomes too soft, which makes handling difficult, and also deteriorates the bondability. Therefore, the upper limit of the heating temperature must be suppressed to 500 ° C.

The aluminum-clad steel sheet obtained by joining and rolling under the above conditions was then heated at 250 to 450 ° C.
It is preferable to perform a heat treatment for 5 minutes or more, and this heat treatment promotes interdiffusion between aluminum and carbon steel, thereby exhibiting higher bonding strength.

In this case, the heating (heat treatment) temperature is 250 ° C.
If it is less than 1, the heat treatment takes too long due to the low speed of the interdiffusion, while if it is heated to a high temperature exceeding 450 ° C., the interdiffusion will proceed too much to form an intermetallic compound, conversely lowering the bonding strength. Therefore, the heating temperature is 250-4
Although it was set to 50 ° C., it is preferable to adjust the temperature to 300 to 400 ° C.

If the heating and holding (heat treatment) time in the heat treatment is less than 5 minutes, sufficient interdiffusion is not performed, and the intended purpose cannot be achieved. However, since the heat treatment for more than 90 minutes leads to the deterioration of the work efficiency and the possibility that the interdiffusion may proceed too much to lower the bonding strength, the heating holding time is preferably set to 5 to 90 minutes. .

Next, the present invention will be described more specifically with reference to examples.

【Example】

Example 1 First, a pure aluminum coil (a material equivalent to A1050) having a thickness of 1.2 mm and a width of 250 mm, and a thickness of 0.3 mm were used.
A carbon steel coil (a material equivalent to SPCC) having a width of 230 mm and a width of 230 mm was prepared.

Next, using these materials, a joining test was performed in a processing line shown in FIG. 2 to conduct a production test of an aluminum clad steel sheet. That is, in FIG. 2, the carbon steel sheet 1 and the pure aluminum sheet 2 are rewound, and the polishing brush 3,
After the surface of the joint is roughened and activated by brushing, the pure aluminum plate 2 is
On the other hand, the carbon steel sheet 1 is heated by energizing between the electric heating pinch rolls 5 and 6. continue,
The heated carbon steel sheet 1 and the pure aluminum sheet 2 are superimposed on each other, pressed by bonding and rolling by a rolling mill 7 and wound up as an aluminum clad steel sheet 8. The rolling conditions at this time were as shown in Table 1.

[0019]

[Table 1]

As is clear from the results shown in Table 1, when the joining rolling is performed under the conditions specified in the present invention, an aluminum-clad steel sheet having a sufficiently excellent joined state and good formability is obtained. But the rolling conditions do not satisfy the conditions specified in the present invention (Comparative Example)
It can be seen that the performance of the obtained aluminum clad steel sheet is not sufficient. The "temperature transition pattern of the carbon steel sheet until the joining rolling" according to the comparative example was categorized and illustrated in FIGS. 3, 4, and 5, respectively.

Example 2 Two of the aluminum-clad steel sheets prepared in Example 1 (test numbers 5 and 14 in Table 1) were degreased and washed, and then heat-treated under the conditions shown in Table 2. Was given. After the heat treatment, a torsional test was performed to investigate the joining property and formability of the aluminum clad steel sheet.

In the torsion test, a test piece (width: 5 mm, length: 150 mm) as shown in FIG. 6 (plate thickness is as rolled) is taken, and grip portions at both ends of 20 mm are shown in FIG. Twisted four times by sandwiching it with the chuck of a torsion tester, and then twisted back eight times in the opposite direction.

Here, the evaluation points of the joinability and formability by the torsion test are as follows. If the bonding is weak, peeling will occur. Therefore, the bonding property can be evaluated based on the presence or absence of peeling. In other words, the weaker the joint, the more the film is peeled off with a small amount of torsional rotation. Therefore, if it can withstand twisting (four times) and untwisting (eight times), the joining property is sufficiently high, and it can be said that it can withstand considerable processing. Since the elongation of the material increases as the number of times of formability torsion increases, when work hardening is large and annealing is insufficient, breakage occurs without peeling due to torsion. Therefore, the moldability can be evaluated by this.

Therefore, the evaluation is "no peeling / breakage" is best, and the next is "breakage", which has a high bondability but a slightly inferior moldability.
Therefore, "peeling" with low bonding property is the worst. Table 2 shows the results of the investigation together with the heat treatment conditions.

[0025]

[Table 2]

As is evident from the results shown in Table 2, according to the method of the present invention, an aluminum-clad steel sheet having excellent bonding properties and formability can be obtained. Test number 29, 3 not satisfied
Brittle intermetallic compound F in clad steel sheets according to 1, 32 and 33
Since e ₂ Al ₅ and Fe ₄ Al ₁₃ were generated at the interface, peeling occurred during the heat treatment.

[0027]

As described above, according to the present invention, it is possible to stably mass-produce aluminum-clad steel sheets having high joining strength and excellent formability, and thus have industrially useful effects. It is.

[Brief description of the drawings]

FIG. 1 is a graph illustrating “an example of temperature transition of a carbon steel sheet until joining rolling” according to the present invention.

FIG. 2 is an explanatory diagram relating to a production line for an aluminum-clad steel plate employed in an example.

FIG. 3 is a graph illustrating an example of a “temperature transition pattern of a carbon steel sheet until joining rolling” according to a comparative example.

FIG. 4 is a graph illustrating another example of “temperature transition pattern of carbon steel sheet until joining rolling” according to a comparative example.

FIG. 5 is a graph illustrating still another example of “temperature transition pattern of carbon steel sheet until joining rolling” according to a comparative example.

FIG. 6 is an explanatory view of a torsion test piece.

FIG. 7 is an explanatory diagram of a torsion test by a torsion tester.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Carbon steel plate 2 Aluminum plate 3 Polishing brush 4 Induction heating coil 5 Electric heating pinch roll 6 Electric heating pinch roll 7 Rolling machine 8 Aluminum clad steel plate

 ──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-5-329665 (JP, A) JP-A-5-69161 (JP, A) JP-A-3-271358 (JP, A) JP-A-3-271358 258471 (JP, A) JP-A-64-5683 (JP, A) JP-A-63-157774 (JP, A) JP-A-59-185588 (JP, A)

Claims (2)

(57) [Claims] When producing a clad plate by laminating a carbon steel plate and an aluminum plate and rolling and pressing them, the carbon steel plate is heated to 170 to 250 ° C.
While the aluminum sheet heated to 00 ° C is superimposed and bonded and rolled in a temperature state in which the temperature of the carbon steel sheet does not fall below 170 ° C, the temperature of the carbon steel sheet until it is heated and rolled is 170 ° C or more. A method for producing an aluminum-clad steel sheet, wherein a time in a state is limited to 2 minutes or less. 2. When a carbon steel sheet and an aluminum sheet are overlapped and rolled and pressed to produce a clad sheet, the carbon steel sheet is heated to 170 to 250 ° C.
While the aluminum sheet heated to 00 ° C is superimposed and bonded and rolled in a temperature state in which the temperature of the carbon steel sheet does not fall below 170 ° C, the temperature of the carbon steel sheet until it is heated and rolled is 170 ° C or more. After performing the joining and rolling while limiting the time in the state to 2 minutes or less, heat-treating the press-bonded clad plate at a heating temperature of 250 to 450 ° C. and a holding time of 5 minutes or more, aluminum Manufacturing method of clad steel sheet.